/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */

package com.zhs.gccs.utils.zip.extra;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.zip.ZipException;

/**
 * This is a class that has been made significantly smaller (deleted a bunch of
 * methods) and originally is from the Apache Ant Project
 * (http://ant.apache.org), org.apache.tools.zip package. All license and other
 * documentation is intact.
 * 
 * ZipExtraField related methods
 * 
 */
// CheckStyle:HideUtilityClassConstructorCheck OFF (bc)
public class ExtraFieldUtils {

	private static final int WORD = 4;

	/**
	 * Static registry of known extra fields.
	 * 
	 * @since 1.1
	 */
	private static final Map<ZipShort, Class<?>> implementations;

	static {
		implementations = new ConcurrentHashMap<ZipShort, Class<?>>();
		register(AsiExtraField.class);
	}

	/**
	 * Register a ZipExtraField implementation.
	 * 
	 * <p>
	 * The given class must have a no-arg constructor and implement the
	 * {@link ZipExtraField ZipExtraField interface}.
	 * </p>
	 * 
	 * @param c
	 *            the class to register
	 * 
	 * @since 1.1
	 */
	public static void register(Class<?> c) {
		try {
			ZipExtraField ze = (ZipExtraField) c.newInstance();
			implementations.put(ze.getHeaderId(), c);
		}
		catch (ClassCastException cc) {
			throw new RuntimeException(c + " doesn\'t implement ZipExtraField");
		}
		catch (InstantiationException ie) {
			throw new RuntimeException(c + " is not a concrete class");
		}
		catch (IllegalAccessException ie) {
			throw new RuntimeException(c + "\'s no-arg constructor is not public");
		}
	}

	/**
	 * Create an instance of the appropriate ExtraField, falls back to
	 * {@link UnrecognizedExtraField UnrecognizedExtraField}.
	 * 
	 * @param headerId
	 *            the header identifier
	 * @return an instance of the appropriate ExtraField
	 * @exception InstantiationException
	 *                if unable to instantiate the class
	 * @exception IllegalAccessException
	 *                if not allowed to instantiate the class
	 * @since 1.1
	 */
	public static ZipExtraField createExtraField(ZipShort headerId) throws InstantiationException, IllegalAccessException {
		Class<?> c = implementations.get(headerId);
		if (c != null) {
			return (ZipExtraField) c.newInstance();
		}
		UnrecognizedExtraField u = new UnrecognizedExtraField();
		u.setHeaderId(headerId);
		return u;
	}

	public static ZipExtraField[] parseA(byte[] data) throws ZipException {
		List<ZipExtraField> v = parse(data);
		ZipExtraField[] result = new ZipExtraField[v.size()];
		return v.toArray(result);
	}

	/**
	 * Split the array into ExtraFields and populate them with the given data as
	 * local file data, throwing an exception if the data cannot be parsed.
	 * 
	 * @param data
	 *            an array of bytes as it appears in local file data
	 * @return an array of ExtraFields
	 * @throws ZipException
	 *             on error
	 */
	public static List<ZipExtraField> parse(byte[] data) throws ZipException {
		List<ZipExtraField> v = new ArrayList<ZipExtraField>();
		if (data == null) {
			return v;
		}
		int start = 0;
		while (start <= data.length - WORD) {
			ZipShort headerId = new ZipShort(data, start);
			int length = (new ZipShort(data, start + 2)).getValue();
			if (start + WORD + length > data.length) {
				throw new ZipException("bad extra field starting at " + start + ".  Block length of " + length + " bytes exceeds remaining" + " data of " + (data.length - start - WORD) + " bytes.");
			}
			try {
				ZipExtraField ze = createExtraField(headerId);
				ze.parseFromLocalFileData(data, start + WORD, length);
				v.add(ze);
			}
			catch (InstantiationException ie) {
				throw new ZipException(ie.getMessage());
			}
			catch (IllegalAccessException iae) {
				throw new ZipException(iae.getMessage());
			}
			start += (length + WORD);
		}
		return v;
	}

	/**
	 * Merges the local file data fields of the given ZipExtraFields.
	 * 
	 * @param data
	 *            an array of ExtraFiles
	 * @return an array of bytes
	 * @since 1.1
	 */
	public static byte[] mergeLocalFileDataData(List<ZipExtraField> data) {
		int regularExtraFieldCount = data.size();

		int sum = WORD * regularExtraFieldCount;
		for (ZipExtraField element : data) {
			sum += element.getLocalFileDataLength().getValue();
		}

		byte[] result = new byte[sum];
		int start = 0;
		for (ZipExtraField element : data) {
			System.arraycopy(element.getHeaderId().getBytes(), 0, result, start, 2);
			System.arraycopy(element.getLocalFileDataLength().getBytes(), 0, result, start + 2, 2);
			byte[] local = element.getLocalFileDataData();
			System.arraycopy(local, 0, result, start + WORD, local.length);
			start += (local.length + WORD);
		}
		return result;
	}
}
